Lead Underpotential Deposition on Pt-submonolayer Modified Au(111)

Abstract

Abstract Lead underpotential deposition on Au(111) surface modified with submonolayer of Pt is studied using cyclic voltammetry and in situ scanning tunneling microscopy methods. The two-dimensional Pt submonolayers (nanoclusters) on Au(111) were obtained by spontaneous Pt deposition on Au(111) from × 103 M {PtCl6}2− + 0.1 M HClO4 solution. The in situ scanning tunneling microscopy data were analyzed using statistical image processing algorithm which enabled quantification of the morphology change on Pt-modified Au(111) surface as a function of applied underpotential. The results suggest that Pb underpotential deposition starts on Au steps and other surface defects, similar to Pb underpotential deposition on Au(111). The further process proceeds by Pb monolayer nucleation and growth on Au terraces into a complete layer. In parallel, the Pb monolayer starts to nucleate on top of the Pt nanoclusters. The final stage of the Pb underpotential deposition is formation of the compact Pb nanoclusters/layer on top of the pre-existing Pt nanoclusters. The scanning tunneling microscopy data suggests that morphology of underpotentially deposited Pb monolayer on Pt-modified Au(111) is similar to the starting surface in terms of the areal density of nanoclusters, their size and shape. The morphological changes of the Pt modified Au(111) surface during Pb underpotential deposition are correlated with cyclic voltammetry results.